Linearized mooring line stiffness matrix

Dear @Jason.Jonkman ,
Is there any doc to read in order to know how you linearize the mooring line stiffness matrix ?

Thank you in advance

Hi Riad,

I use pyMAP to linearize the mooring system’s stiffness matrix. pyMAP is the python version of Map++. And it can read OpenFAST primary file (.fst) where Map++ primary file is included. I feel it is convenient to use pyMAP to output mooring stiffness matrix.
You can download and install pyMAP from below link:

Below link is a example how to extract mooring stiffness matrix using fst file:

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Dear @Ran.Tu ,

Thank u for your suggestion. I will try it :grin:

Dear @Jason.Jonkman,

I notice also that in “Definition of the floating system for phase iv of oc3”, you said that OC3 is held by 3 catenary mooring lines of type “crowfoot” (delta connection).
But when i run map input file, it appears as no delta connection and its simply one line from the fairlead to the anchor.
Is it correct? Could you explain why you did this ?
The photo where the mooring lines appear is below:

Thank you in advance


Dear @Riad.Elhamoud,

When the OC3-Hywind spar was first modeled in FAST v7, the quasi-static mooring line model used by FAST v7 was simplified and only permitted lines that connected from the floating platform to the seabed, without line-to-line interconnections such as delta connections. Instead, the yaw stiffness associated with the delta connection of the mooring system was considered by adding a yaw spring to the FAST v7 model. Of course, line-to-line interconnections are possible to simulate in MAP++ and MoorDyn within FAST v8 and OpenFAST, but some implementations of the OC3-Hywind spar model still make use of the old FAST v7 convention.

Best regards,